Table 1.

Participant Eligibility Criteria by Group

Groups	Population	Eligibility Criteria
All	All Participants	Aged 18 or older English speaking Visit at least one active online health community focused on an illness or medical condition1 Not employed in healthcare or pharmaceutical industries Community participation is not part of job
1-3	General Users	Visit community at least once per month
4-5	Active / Heavy Users	More likely to post information on site than read it Visit community at least once per week
6-7	Passive / Light Users	More likely to read information on site than post it Visit community at least once per month but less than once per week
8	Recent Diagnosis (Fibromyalgia)	Diagnosed with fibromyalgia within last 12 months (or family member diagnosed in last 12 months) Visit a community focused on fibromyalgia at least once per month
9	Recent Treatment Decision (Depression)	Diagnosed with clinical depression (or family member diagnosed) Made a major treatment decision related to depression within last 12 months Visit a community focused on depression at least once per month
10	Single Community (Multiple Sclerosis)	Diagnosed with multiple sclerosis (or family member diagnosed) Visit the PatientsLikeMe MS community at least once per week

¹We verified that OHCs were active and eligible by visiting OHC URLs provided by potential participants. We confirmed that site content was mostly or exclusively member-generated, posted within the last week, and focused on a specific medical condition.